Brief History:
The Advocator-class Star Dreadnought was engineered in 11 BBY to bridge the gap between the Mandator I/II-class and Lodestar-class ships and other older dreadnoughts. Their main function was to replace those aging ships for front-line combat duty while the Executor-class was being constructed. It is a Kuat Drive Yards design of which only seven were ever built, as that number served the purposes of the Empire as they waited for newer craft to come from Galactic shipwrights. Once a few of the Executor-class ships were ready, the Empire mothballed and dismantled the Advocator-class so its materials could be reused. However, over the six or seven years of its existence, it proved to be a tough and versatile command ship (usually within a convoy), well-suited to long tours of duty subjugating worlds in the Mid and Outer Rim._________________The only words of explanation you need for any concept in the entire Star Wars universe are the words Science Fiction and Space Opera.